nx_tls13_hello_test.nx

nx_tls13_hello_test.nx -- structural + iterator KAT for the ClientHello emitter + ServerHello parser + extensions iterator. We don't pin to RFC 8448 §3 ClientHello bytes because that vector uses a specific extension ordering + a different cipher-suite list + includes extensions we don't yet ship (padding, psk_kex_modes). Instead we verify: A. Emit succeeds + total length matches spec formula B. Handshake header is well-formed: msg_type=1, uint24 length equals total - 4 C. Body fields land at the expected offsets: legacy_version, random (round-trip), session_id (empty), cipher_suites (3 TLS 1.3 standard suites in canonical order), compression D. Extensions list length matches actual sum of emitted extensions E. Iterator finds each of the 5 extensions by type F. server_name extension contents includes our SNI hostname G. key_share extension contents includes our pubkey H. Re-parse as ServerHello (similar structure -- cipher_suite is single not list, so we use a hand-built mini-ServerHello) verifies the parser's structural walk works expect_exit: 0 license_tier: ORIGINAL